What is an absolute encoder What is an incremental encoder

What is an absolute encoder? What is an incremental encoder?

Encoder is a kind of electrical signal device, which is converted by angular and linear displacement. The encoder is divided into two parts: code disc and code ruler, which can be divided into contact type and non-contact type according to the way of reading. But according to the working principle, it can be divided into absolute encoder and incremental encoder. Now let's understand the working principle of absolute encoder and incremental encoder and what is the difference between them?

Absolute encoder

The absolute encoder is a sensor that indirectly outputs digital data. Above its circular code disc, there are several concentric code discs along the radial direction. Each channel is composed of uniform and uneven sector areas, and the sector tree of adjacent code channels is a double sector. The number of code channels on the code wheel is the number of bits in its binary number. One side of the disk surface is the light source, and the other side is a photosensitive element corresponding to each channel. When the board is in a different position, each photosensitive element converts the corresponding level signal according to whether it is illuminated or not to form a binary number. The characteristic of this kind of encoder is that it does not need a counter and can read the specific digital code corresponding to any position of the shaft. It seems that there must be no way. At present, there are 16-bit absolute encoder products in China.

Incremental encoder

The incremental encoder converts the displacement into a periodic electric signal, and then converts the electric signal into a counting pulse. The number of pulses represents displacement. When the shaft of the incremental encoder rotates, there is a corresponding pulse output. Through the previous direction judgment circuit and counter to realize the judgment of the rotation direction and the increase or decrease of the number of pulses. The starting point of counting can be set arbitrarily, which can realize unlimited accumulation and measurement of multiple circles. The Z signal of one pulse per revolution can also be used as a reference mechanical zero position. When the encoder rotates once, it outputs a specific pulse, and the number of pulses is determined by the number of lines of the encoder's grating. When the resolution needs to be improved, the A and B signals with a phase of less than 90 degrees can be used to double the original pulse number, or the high-resolution encoder can be replaced.

What is an absolute encoder? What is an incremental encoder? What is the difference between an incremental encoder and an absolute encoder?

First of all, the principle of the encoder is different

1. Incremental encoder: An equal angular gap is opened on the edge of the code wheel (divided into two parts, uniform and uneven), and the light source and photosensitive element are installed on both sides of the encoder. When the code wheel rotates along the working dimension, every time it rotates a slot, the light and shadow will change.

After shaping and amplifying, an output signal with a certain amplitude and power can be obtained, and the number of pulses is equal to the number of rotating slots. The pulse signal is sent to the counter to count, and the rotation angle of the sphere can be known according to the measured number.

2. Absolute encoder: Due to its low accuracy and small output bits, if parallel output is still used, the output signals must be well connected. For simpler cases, isolation and extra cable cores will bring a lot of convenience and reduce reliability.

Therefore, absolute encoders have multiple digits. The output type is usually serial output or bus output. The serial output of the German absolute encoder is the most common synchronous serial output.

Second, the nature of the encoder's work is different

1. Incremental encoder: Convert the displacement into a periodic electric signal, and then convert the electric signal into a counting pulse, and use the number of pulses to express the displacement.

2. Absolute encoder: Since each position is absolutely unique, anti-interference, no power-down memory, it has been more and more commonly used in angle and length measurement and positioning control in various industrial systems.

The above is about okplazas.com encoder: What is an absolute encoder? What is an incremental encoder? As well as related introductions about their previous relationships and differences, friends who are interested are welcome to exchange and learn together.